Flow meter



E. E. LIBMAN ETAL 2,826,915

FLOW METER Filed Jan. 1 8, 1954 IN V EN TOR.

WILL/AM Woc/rEN-us BY EAR/ E. L/MA/v A TTR NE Y March 18, 1958 FLOW METER Application January 18, 1954, Serial No. 404,637

3 Claims. (Cl. 73-7-228) This invention relates to iiow meters, and it is concerned particularly with improvements for enabling rates ,of ow to be measured in terms of weight rather than volume. Y

Flow meters customarily are designed to measure the volumetric rate at which a fluid is owing. In some of the modern applications of ow meters it is more desirable that the rate of flow be measured in units of weight. For example, in the operation of jet aircraft it is more important to know the weight of fuel being consumed per unit of time than to know how many gallons Iare being consumed per unit of time. Conventional measuring methods are such that the consumption of fuel `by weight must be computed from its consumption by gallons or other units of volume, which is inconvenient.

One of the principal objects of our invention is to provide an improved flow meter which directly measures Irates of flow according to weight.

Another object of our invention is the provision of an improved flow meter which is capable of being placed directly into the passage through which the uid ows Without constricting or aecting its rate of flow.

Still another object of our invention is to provide a ilow meter which employs an element of high sensitivity and one which will respond accurately to pressures exerted by the fluid as it passes through the flow meter.

A further object of the invention is the provision of a flow meter which is simple in design and one having indicating means readily settable to correspond with the luids Ibeing used.

' Other objects of the invention will ybe pointed out in the following description and claims and illustrated in the accompanying drawings, which disclose, by way of examples, the principle of the invention and the best mode, which has been contemplated of applying that principle.

In the drawings:

Fig. 1 is a sectional view yof a ilow meter constructed in accordance with the principles of the invention.

Fig. 2 is a circuit diagram of a highly sensitive strain gauge which is incorporated in the apparatus to operate the indicating means.

The ow meter of the present invention comprises a iluid inlet to which a fluid outlet 11 is connected so as to form a fluid passage and a bend in the passage. In the disclosed embodiment the bend is formed by connecting the inlet 10 and the outlet 11 at an angle normal to each other. A iiuid passing around the bend will undergo a change in direction of its velocity and as a result create changes in its vector momentum.

Positioned in the passage formed by the inlet 10 and the outlet 11 and at the connection of the same is a movable piston 12. The piston 12 is housed in housing 13 and is limited in rotation and axial movement by the pin 14. In the embodiment shown in the drawings housing 13 can be formed as an extension of the inlet 10. The piston 12 is provided with a curved surface 15 so that when it is in proper position as shown in Fig. 1 it will complete the bend of the connected inlet 10 and `outlet 11 to divert ,United States Patent the uid from the inlet to the outlet. Diversion at the connection by the piston 12, of the uid passing therethrough, will also, as a part of the connection, create changes in the momentum of the fluid. Since the piston 12 is permitted axial movement by the pin 14, it will be kmoved by the changes in momentum which the iluid un- A'dergoes as it ows around the bend.

'ing 13 in back of piston 12 and between the piston and pressure plate 16 is the spring 17. Adjusting screw 18 and attached thumb piece 19 facilitate easy tension adjustment of the spring 17. At the rear or back end of housing 13 is a closure member 20 which, for ease of assembly, is screw threaded into the housing. In the embodiment as shown the adjusting screw 1S is guidingly supported by theV closure member 20 and the area thereabout is made uid tight by a seal ring 21 held in place by plug 22.

To aid the operation of the spring 17 and to prevent the generation of spurious results due to static pressure conditions, the inlet .port of a conduit 23 is positioned normal to the flow of uid in the passage in the area in which inlet 10 and outlet 11 are connected. This area of connection of inlet 10 and outlet 11 will fall within the dot-dash lines which define the angle A. The other end or outlet port of the conduit 23 is positioned to have its outlet opening -behind the piston 12. Openings 24 in the plate 16 allow the fluid to pass therethrough so that changes in static pressure are communicated to the back of the piston 12.

The piston 12, forming a part of the bend is therefore movable in response to the changes in momentum of strain member 25 attached at one end to the leg of the `L-shaped member 26 and at its other end to a similar member 27. Strain member 25 is' suspended tautly between the legs of the L-shaped members 26 and 27 when the same are attached to their respective supports, piston 12 and closure Z0.

, Shown in Fig. 2 is the electrical arrangement utilized to indiacte the ilow of uid through the meter. Indicator 28 is operated bythe changes in resistance in the strain member 25 which Yis formed as an arm of the Wheatstone bridge arrangement. Variable resistor 29 and resistors R complete the Wheatstone bridge. By proper adjustment of spring 17 and setting of the variable resistor 29 the zero setting of the indicator 28 can be controlled to read zero `at zero ow. The indicator may then be calibrated to show the consumption of the fluid in weight per unit of time by the rate of ow.

The flow meter is easily set-up for operation. At zero ow, the spring 17 and variable resistor 29 are adjusted so that indicator 28 will read zero consumption. When the fluid is introduced into the meter through inlet 10, as it encounters the bend formed in the passage by the connection with outlet 11 and surface 15 of piston 12, it undegroes changes in its vector momentum. The changes in momentum tend to move the piston 12 rearwardly and out of the path of the fluid. As a consequence of the movement of the piston 12, strain member 25 will be tensioned or strained to result in a variation in its resistance and an unbalancing of the Wheatstone bridge. When the Wheatstone bridge is unbalanced indicator 28 will give a true reading of the ow of iluid through the meter in weight per unit of time.

Throughout the description the inlet 10 and the outlet 11 have been described as being connectedf It is not intended that the term connected be used in its strict sense, but more nearly to show that both the inlet 10 and the outlet 11 form a continuous iluid passage. Although 'they 'mayfbe separate" members joined together in some well- 'known manner, it` isalsor `possible thatwtheyA may both be indivisible portions of a bent pipe with the housing 13 attached tonor casf'integral with the same. In

only of the' area lgenerally designated by the angleA It is'tapp'arent/from the foregoing thatthe'presentdevice! is 'quite `simple'toset`Aup`15011opt-ration?andltbati ed in the second of said aligned branches for deecting t the wilow4 of uid' fromv lsaid "inlet passage tosaid outlet once it is lset up properly,fit"` will`be consistently accurate. Y

described with particular reference to 'aircraft operation, 'this shouldnot be regarded as 'limitingftheinventionin Vany "way' It is obvious that the invention will-have'utility wherever itis'idesired tofm'easure the'V4 rate at which a fluid is flowing in terms of weight per unitlofA time. Moreover, it vshould be noted `thatthe term iluid is' not Vrestricted to liquids only. Y

'While there have been shown `and described andpointed out the fundamental novel features of the-invention as applied toa preferred embodiment thereof, itwillbe understood that various omissions and substitutions and changes inthe form and details of the deviceillustrated and in`` its operation 4may be `made by those skilled in the art, :without `departingf'irom the spirit ofthe invention. lt isthe intentior'i;threfore; to be lirnited'only asindilcated, byjthe scope r` i1he^clairns` appended'hereto.

The invention isicl'aimed as follows: y

1'. Aovv` meter comprising a substantially 'T-shaped housingdhaving two aligned branches and a third branch perpendicularly"related" thereto,` 'one of "sad aligned branches and said `third branc1f"a1ordingl inlet and outlet passages'for fluid, a movable memberslidably' gmided in the second of said aligned branches" of said'housing and arranged to move in response to the 'change'inmomentum of uid owingfrom said inlet passageA to ,said outlet passage, a conduit interconnectingsaid rst branch with said `second branch to neutralize static pressures, resilient means tending 'to` oppose the movement of `said movable member, 'and an electrical strain'gaugecoupled tov said movable member and to said secndfjaligncd `'banchof said housing to detect displacement of' said -movable"meniben 4 2, A ow metercomprising a substantially `T'lshape'd housing having two aligned branches and' athird .branch perpendicularly" related/thereto, one" of said aligned branches and-.said `third`bra11ch` affording] inlet and `outlet passages foruid, a deecting member slidablylguidpassage, said deiiecting means being arranged to move in said second branch in response to the change in the momentum of the fluid as the uid ilow is deflected, means in said second branch for yieldingly opposing the movement of said deectingfmember, a conduit interconnect ing said iirst branch with said second branch on oppo site sides of said detieeting member to neutralize static pressurea strainmember inrsaid second branch .coupled between :said delleeting'member `and atixed position in `said second branch t0=detect.:displacement of ,said::de-

fleeting memberand electrical bridge means coupled to saidstrain member to' detect changes in the electrical characteristics of said? strain member.

3. A ow meter comprising a substantially T-shaped housing having two aligned branches and a third branch perpendicularly related thereto, one of said aligned branches and said'third' branch" affording inlet and out- 'letpa'ssages for'iluid, a piston'slidably` guided in the'second ofsaid aligned branches having-a curved front surface for deiiecting the ow of uid from said inlet`-pasvsagev to'said outIebpaSSage, Asaid piston 4being arranged to'I slide inlsaid second branch in response to the change inI the 'momentum offthe'uid asV the uidfowis deected,

-spring tensionmeansyinsaid second branch for'yieldably opposing-said movementofisaid piston, 'a conduit communicating at' its ends with the'interior of said hous- -ing on oppositelsides of said'piston for equalizingv static y.pressure, a isupporting memberV` extending rearwardly from the back ofsaidipiston, a strainrmember' having oneWendconnectedtothe extremity of said supporting member and= its other 'end attached to a fixed position 'in'saidA second branch so Athat movement ofsaid piston 'strains said strain'member in accordance with the-momentum of the tluid llow, said strain member having a fresistaneef to` theiiowA of electric4 currentY which varies in accordance withthestrain on'said member, and elec- "tricalb'ridge `means coupled to said strained member to detect changes inthe resistance thereof.

AlReferences' 'Cited in thele of this patent UNITEDv STATES PATENTS 

